Effect of Sensory-Amplitude Electric Stimulation on Motor Recovery and Gait Kinematics After Stroke: A Randomized Controlled Study

Participants 

The trial included 30 consecutive inpatients with hemiparesis after stroke who met the study criteria. Patients were required to meet the following criteria for inclusion in the study: (1) first episode of unilateral stroke with hemiparesis during the previous 6 months, (2) a score between 1 and 3 inclusive on Brunnstrom stages of the lower extremity, (3) ability to understand and follow simple verbal instructions, (4) ambulatory before stroke, (5) no medical contraindication to walking or to electric stimulation (having pacemaker or venous thrombosis at the paretic leg), and (6) ability to stand with or without assistance and to take at least 1 or more steps with or without assistance. The mean age ± standard deviation (SD) was 63.2±9.7 years, and the mean time since stroke was 3.4±2.1 months. Stroke was defined as an acute event of cerebrovascular origin causing focal or global neurologic dysfunction lasting more than 24 hours and diagnosed by a neurologist and confirmed by computed tomography scan or magnetic resonance imaging. The protocol was approved by the Ankara University Ethics Committee.

Design 

A double-blind, randomized, controlled design was used. The patients and the physician (GY) who performed the outcome measures were blinded to the use of SES but not the therapist who delivered the electric stimulation. Patients were randomly assigned to 1 of the 2 groups after initial evaluation. We used the block randomization method to ensure an equal number of patients in each group. Blocks were numbered, and then a random-number generator program was used to select numbers that established the sequence in which blocks were allocated to one or the other group. A medical resident who was blinded to the research protocol and was not otherwise involved in the trial operated the random-number program. After randomization, 15 patients were assigned to the placebo group (conventional rehabilitation program plus sham SES), and the remaining 15 were assigned to the SES group (conventional rehabilitation program plus SES) (fig 1).

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Fig 1. Flow diagram for randomized subject assignment in this study.

Intervention 

All subjects participated in a conventional stroke rehabilitation program delivered by multiple therapists 5 days a week, 2 to 5 hours a day, for 4 weeks. The conventional program is patient specific and consists of neurodevelopmental facilitation techniques, physiotherapy, occupational therapy, and speech therapy (if needed). The SES group also received 30 minutes of SES once daily 5 days a week for 4 weeks to the common peroneal nerve of the paretic leg. Two 6×8mm “sponge”-type electrodes with rubber carriers were placed on the anatomic localization of the common peroneal nerve (just below the capitulum fibulae of the lower leg) and on the belly of the tibialis anterior muscle while the patients were in supine position.18 A Sonopuls 992a was used to deliver the asymmetric biphasic rectangular stimulation at a frequency of 35Hz with a pulse width of 240μs. The stimulation amplitude was adjusted at each session to the point in which the patient perceived a mild tingling sensation (≈10mA) but below an observable or palpable muscle contraction. A duty cycle of 10 seconds on and 10 seconds off was used to minimize sensory habituation.16 The same setup was used for the placebo group without any stimulation. The machine was turned on so that there was a light to indicate that it was in operation. Patients in the placebo group were not told that they would feel the stimulation. The same therapist delivered the SES or sham stimulation.

Outcome Measures 

Outcome measures were performed by the same investigator (GY) 1 to 3 days before and after the 4 weeks of the treatment period in the rehabilitation ward.

Lower-Extremity Motor Recovery 

Lower-extremity motor recovery was assessed by using the Brunnstrom stages for the lower extremity.19 The 6 grades of the Brunnstrom stages for the lower extremity are as follows: (1) flaccity, (2) synergy development (minimal voluntary movements), (3) voluntary synergistic movement (combined hip flexion, knee flexion, and ankle dorsiflexion, both sitting and standing), (4) some movements deviating from synergy (knee flexion exceeding 90° and ankle dorsiflexion with the heel on the floor in the sitting position), (5) independence from basic synergies (isolated knee flexion with the hip extended and isolated ankle dorsiflexion with the knee extended in the standing position), and (6) isolated joint movements (hip abduction in the standing position and knee rotation with inversion and eversion of the ankle in the sitting position). The Brunnstrom stages were chosen because it reflects underlying motor control based on clinical assessment of movement quality. In the lower extremity, voluntary ankle dorsiflexion is a stand point indicating the achievement of selective motor control.19 Once voluntary movement is achieved, synergistic patterns are then modified to selective (out of synergy) patterns. Brunnstrom stages I through III indicate more synergistic and mass movements, whereas stages IV through VI indicate isolated and selective movements. Patients were classified into 2 subgroups in terms of motor stage (ie, those with none [Brunnstrom stages ≤ III] versus those with some [Brunnstrom stages ≥ IV] selective motor control).20

Gait Kinematics 

Walking velocity; step length; percentage of stance phase at the paretic side; sagittal plane kinematics of the pelvis, hip, knee, and ankle; maximum ankle dorsiflexion angle at swing; and maximum ankle plantarflexion angle at initial contact were selected as outcome parameters. Three-dimensional gait data were collected with the Vicon 370 systemb and processed by the Vicon Clinical Manager (version 3.2) software. Anthropometric data including height, weight, leg length, and joint width of the knee and ankle were collected. Fifteen passively reflective markers were placed on the following standard and specific anatomic landmarks: sacrum, bilateral anterior superior iliac spine, middle thigh, lateral knee (directly lateral to axis of rotation), middle shank (the middle point between the knee marker and the lateral malleolus), lateral malleolus, heel, and forefoot between the second and third metatarsal head.21 Subjects were instructed to walk at a self-selected speed over a 10-m walkway during which data capture was completed. Five cameras recorded (at 60Hz) the 3-dimensional spatial location of each marker as the subject walked. The best data of 3 trials were used in analysis. The trial in which all the markers were clearly and automatically identified by the system was determined as providing the best data.

Statistical Analysis 

Data were analyzed by using SPSSc for Windows. The percentage change between pre- and posttreatment data for both groups was calculated as: 100 × (pretreatment − post-treatment)/pretreatment.

The group means and percentage changes were compared between the SES and the placebo group by using nonparametric paired and unpaired t tests. The chi-square test was used to compare the groups in terms of the number of patients with Brunnstrom stages for lower extremity I through III or IV through VI. We preferred nonparametric statistics because of the abnormal distribution of the data. Significance was set at .05.

Lower-Extremity Motor Recovery 

There was a statistically significant improvement in pre- to posttreatment mean Brunnstrom scores in both groups (P<.05). However, the difference between the 2 groups in terms of the percentage change was not significant (table 2). In total, 60% (n=9) of the patients in the SES group and 53% (n=8) of the patients in the placebo group improved from Brunnstrom stages (I−III) to Brunnstrom stages (IV−VI). The between-group difference of the percentage change was not significant (P>.05) (table 3).

Table 2. Outcome Measures in the SES Group and the Placebo Group

	Outcome Measures	Pretreatment		Posttreatment
		SES	Placebo	SES	Placebo
	Brunnstrom stages of lower extremity	3.2±1.6	3.3±1.2	4.1±1.4⁎	3.5±0.9⁎
	Walking velocity (m/s)	0.31±0.18	0.36±0.22	0.34±0.11	0.37±0.20
	Step length (m)	0.29±0.11	0.28±0.16	0.32±0.12	0.30±0.12
	% of stance phase (paretic side)	59.1±3.5	58.0±5.5	58.7±4.7	58.9±5.7
	Pelvis (deg)†	13.2±5.7	12.2±3.3	10.3±6.2	11.0±3.1
	Hip (deg)†	16.6±8.6	17.3±10.0	16.9±7.8	17.7±7.9
	Knee (deg)†	25.4±10.2	27.7±14.9	27.9±11.7	28.1±9.8
	Ankle (deg)†	17.1±12.7	16.1±3.8	18.5±4.9	16.6±9.9
	Maximum ankle DF at swing (deg)	−5.9±2.3	−5.8±2.6	−4.6±4.1	−4.3±1.5
	Maximum ankle PF at initial contact (deg)	−1.8±0.9	−3.0±1.5	1.2±7.5	−2.1±1.2

NOTE: Values are mean ± SD Abbreviations: DF, dorsiflexion; PF, plantarflexion.

⁎ P<.05. † Sagittal plane total excursion.

Table 3. Percentage Change After Treatment in the SES Group and the Placebo Group

	Outcome Measures	SES Group (%) (n=15)	Placebo Group (%) (n=15)	P
	Δ Brunnstrom stages of lower extremity	46	44	.31
	Brunnstrom stages from I−III to IV−VI	60	53	.09
	ΔWalking velocity (m/s)	13	13	.97
	ΔStep length (m)	18	19	.34
	Δ% of stance phase (paretic side)	2	1	.60
	ΔPelvis (deg)⁎	12	14	.89
	ΔHip (deg)⁎	4	3	.75
	ΔKnee (deg)⁎	7	3	.44
	ΔAnkle (deg)⁎	16	19	.47
	ΔMaximum ankle DF at swing (deg)⁎	22	25	.44
	ΔMaximum ankle PF at initial contact (deg)⁎	14	12	.70

Abbreviation: Δ, percentage change between pre- and post-treatment.

⁎ Sagittal plane total excursion.

Gait Kinematics 

The mean values ± SD of assessed parameters of the groups at pre- and posttreatment are given in table 2. There was no significant difference between the groups in any of the initial clinical characteristics. Time-distance and sagittal plane gait kinematics were improved in both groups. However, neither the difference between pre- and posttreatment data for each group nor the percentage of change between the groups was significant (see table 3).